Interest-Only vs Principal-and-Interest Comparison

Useful for investment properties or cash-flow-sensitive scenarios; shows IO repayment, the P&I step-up after IO ends and the extra cost vs straight P&I.

s*(1+s)**o/((1+s)o-1)}function n(){var i,a,r,d,u,h,m,c=+t.querySelector("[data-f=loan]").value,l=+t.querySelector("[data-f=rate]").value,n=+t.querySelector("[data-f=years]").value,o=+t.querySelector("[data-f=ioYears]").value;o>=n&&(o=n-1),i=c(l/100/12),a=n-o,r=s(c,l,a),d=s(c,l,n),u=io12+ra12,h=dn*12,m=u-h,t.querySelector("[data-out]").innerHTML='

IO monthly '+e(i)+'

After IO period, repayment rises to '+e(r)+"

Interest-only repayment (first "+o+" yrs)	"+e(i)+"
P&I repayment (remaining "+a+" yrs)	"+e(r)+"
Straight P&I reference	"+e(d)+"
IO path total repayments	"+e(u)+"
P&I path total repayments	"+e(h)+"
Extra cost of IO path	"+e(m)+"

"}t.addEventListener("click",function(e){e.target.dataset.act==="calc"&&n()}),t.addEventListener("input",function(e){e.target.dataset.f&&n()}),n()})()

How to use

Results refresh as you edit the fields — no need to press Calculate. Adjust any input to test alternative scenarios.

Notes

After the IO period the residual principal is repaid over a shorter P&I term, so repayments typically step up noticeably. Lender IO terms and renewal conditions vary.

Related calculators

• All calculators
• Home loan repayment
• Borrowing capacity
• Stamp duty + FHB grant